This invention relates to staple fibers, and more particularly, surface modified polyester staple fibers which are made by a bulked continuous filament (BCF) process, and fiber clusters made from such fibers which can be used as fiber filling material, especially polyester fiberfill.
Polyester fiberfill is widely used as a relatively inexpensive filling material for pillows, quilts, sleeping bags, apparel, furniture cushions, mattresses and similar articles. Fiberfill is mostly produced from polyethylene terephthalate crimped staple. A wide range of such staple is available with different deniers, crimp geometry, crimp level, cut length, surface coating, cross-section and other properties. Polyester fiberfill is often coated with a silicone coating such as a polyaminosiloxane slickening agent and sometimes with other non-silicone slickeners, such as segmented polyethylene terephthalate/polyalkylene oxide. Such coatings improve the softness and the hand of the finished article and also contribute to reduce the tendency of the fiberfill to mat (i.e., to clump together) in the article during use. The overwhelming majority of staple filling fibers are carded and cross lapped to form batts which are then used as the filling material. Alternatively, the staple fibers are opened and blown as filling material in a final article.
Another type of filling material is fiber clusters, which are staple fibers which are formed into clusters before being used as a filling material. Contrary to batts made from staple fibers, fiber clusters can move within a ticking in a similar way to down or down/feather blends. Fiber clusters are currently produced from baled spiral crimp staple, made generally by a two step process (polymerization/spinning, then drawing). The staple fibers are first opened, then submitted to a rolling, or tumbling, action on roller cards, flat cards or by rolling against a wall of a cylinder. Known tumbling processes are disclosed in U.S. Pat. Nos. 4,618,531 and 4,783,364. Fiber clusters have gained acceptance in many filling end-uses in the last decade, and with increased volume and improved manufacturing processes, the price of such fiber clusters has slowly come down. However, the manufacture of fiber clusters is still a relatively low throughput and expensive process compared to carded batts, and this hinders further development of the market.
Crimp plays an essential role in the structure of fiber clusters and the ease of their formation. Moreover, crimp determines the filling power, softness and recovery from compression of fiberfill products. Commercial filling fibers may have either mechanical crimp or helical, or spiral, crimp. Mechanical crimp is produced by well known crimper box technology, while helical crimp is produced by asymmetrical quenching or by bicomponent conjugated spinning. Bicomponent conjugated fibers are produced either by spinning two polymers differing only in molecular chain length or by spinning two different polymers or copolymers. The crimp of these fibers results from differential shrinkage between the two polymers or their bicomponent structure when the fiber is exposed to heat. Halm et al., in U.S. Pat. No. 5,112,684, have demonstrated that fiber clusters for filling uses have been prepared from mechanically crimped fibers with specific configurations. Helical fiber clusters having a helical crimp are disclosed by Marcus in U.S. Pat. Nos. 4,618,531 and 4,783,364.
Practice has shown that helical crimp fibers made by asymmetrical quenching or by bicomponent conjugated spinning are the best feed materials for fiber clusters due to the ease of rolling as well as to the highly desired softness, refluffability and recovery from compression of the resulting fiber cluster filling. Feed fibers made by asymetric quenching or by bicomponent conjugated spinning form fiber clusters with spontaneous curling under low forces. Such fiber clusters have a uniform three dimensional entanglement, optimal bulk, and the best balance of softness and recovery from compression, as compared to fiber clusters formed by mechanical crimping. In addition, fibers which exhibit spontaneous curling produce fiber clusters with relatively few fibers sticking out of the fiber cluster, reducing the cohesion between the clusters. Low cohesion is particularly desirable in articles such as pillows and furniture back cushions, since it improves refluffability. Moreover, spontaneous curling not only improves the fiber cluster structure, but it also increases the cluster manufacturing throughput, by reducing the required rolling time.
Fiber spinning speed is typically much faster than the speeds of drawing/cutting and carding/tumbling processes for manufacturing staple fibers and staple fiber clusters. Under current conditions, matching a fiber spinning line with a staple fiber drawing/cutting process and a fiber cluster manufacturing process is very difficult and not economical. The low throughput processes used for producing fiber clusters according to known processes make it impractical to couple fiber spinning and drawing with fiber cluster production. Moreover, the two-step process for manufacturing staple fiber clusters of polymerization/spinning, then drawing/cutting is a complicated and high-cost process, because the uncoupled process requires extra material handling between process steps. In addition, its manufacturing and investment costs are high because it requires additional labor to operate a separate traditional draw machine, which operation is expensive. Moreover, the draw machine itself is expensive.
Thus, there exists a need for developing a simplified process for producing fibers which can be used to make fiber clusters. In particular, it would be desirable to minimize material handling by coupling the entire fiber/cluster manufacturing facility, including the spinning/drawing/cutting steps, as well as the cluster forming steps. Such a process would, ideally, produce low cohesion fiber clusters and would be much simpler and more economical, from a manufacturing standpoint, than the processes of the prior art.
Continuous jet bulking of yarns is widely used to produce carpet yarns, usually from polyamide or polypropylene. Machines for performing such continuous et bulking of yarns are available in the trade from Neumag of Neumunster, Germany, as well as other machine manufacturers. Neumag""s standard high-speed continuous staple fiber producing line can produce items based on virtually any polymer, including polyester, as disclosed in xe2x80x9cEasy routes to fibre productionxe2x80x9d, ITMA Report: MMF Equipment, Textile Month, December, 1995, pp. 15-20. However, it is not known to us e such a line to produce surface modified staple fiber. Nor is it known to use continuous jet bulking for producing polyester staple fiber for use in fiber clusters.
Applicants have found that polyester staple fibers produced by a bulked continuous filament (BCF) process can form fiber clusters much faster than conventional processes used for making asymetrically quenched or conjugated bicomponent fibers. The structure of such fiber clusters is very similar to the structure of fiber clusters produced from helical fibers, and the filling power of such fiber clusters can be equal to or better than such fiber clusters of the prior art, depending upon the structure of the fiber clusters and the bulking conditions.
Moreover, the BCF process of the present invention enables one to produce fibers with excellent durability and with bulk levels in end products, such as pillows and cushions, which are higher than the bulk levels of products made with cluster of the prior art. Surprisingly, these properties can be achieved under very gently rolling conditions.
Furthermore, the BCF process of the present invention enables one to adjust either the support bulk or the initial height of the end product independently, which is not possible with the prior art. This makes it possible to produce the optimal compression curve for an an end product made from fiber clusters of the present invention.
In addition, the BCF process of the present invention forms fibers at a rate which is much faster than known processes for forming asymmetrically quenched or bicomponent conjugated fibers. In particular, the speeds of the process of the present invention are much faster than those of the prior art. Using the same process conditions for fiber clusters made according to the present invention as compared to fiber clusters made from asymmetrically quenched or bicomponent conjugated fibers, the feed fibers made according to the present invention formed equivalent fiber clusters in two to five times shorter tumbling time. In addition, the process of the present invention allows drawing/crimping and cutting at speeds which are five to twenty times faster than standard spinning/drawing/crimping/cutting technology, resulting in manpower and investment reduction versus traditional routes.
In addition, the availability of small BCF spinning/drawing/bulking units allows further integration of the production of staple fibers and/or fiber clusters from polymer to finished product in a coupled line. The very fast rolling of the feed fibers into fiber clusters helps to match the capacities of spinning/drawing and fiber cluster production, simplifying the process and reducing required investment and manufacturing costs. Moreover, the BCF process of the present invention may be coupled with on-line cutting.
In accordance with the present invention, there is provided a process for producing such fiber. According to this process, a synthetic polymer is spun from a melt of the polymer and cooled to produce solidified continuous filaments. The solidified filaments are drawn as they are advanced by heated rolls. The filaments are jet bulked with a heated dry fluid at a temperature that is above the second order transition temperature of the synthetic polymer and are cooled to below the second order transition temperature of the synthetic polymer. The filaments are cut on line to produce staple fibers. A surface modifer is applied to the fibers. The fibers are then cured. Alternatively, the surface modifier may be applied to the filaments prior to cutting, and then the cut fibers are cured. Also in accordance with the present invention, there is provided a surface modified staple fiber made according to the process of the present invention.
According to another aspect of the present invention, there is provided a surface modified staple fiber. The fiber has a three-dimensional curvilinear random primary crimp. Preferably, the staple fiber is of 2 to 20 dtex and has a cut length of 10-100 mm. The fiber has a secondary crimp with a frequency of more than 6 crimps per 10 cm length. According to another aspect of the invention, there are provided three-dimensional, randomly entangled fiber clusters produced from such fiber.